/* * * Wireless daemon for Linux * * Copyright (C) 2018-2019 Intel Corporation. All rights reserved. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA * */ #ifdef HAVE_CONFIG_H #include #endif #include #include "src/missing.h" #include "src/util.h" #include "src/ie.h" #include "src/handshake.h" #include "src/crypto.h" #include "src/mpdu.h" #include "src/sae.h" #include "src/auth-proto.h" #define SAE_RETRANSMIT_TIMEOUT 2 #define SAE_SYNC_MAX 3 #define SAE_MAX_ASSOC_RETRY 3 enum sae_state { SAE_STATE_NOTHING = 0, SAE_STATE_COMMITTED = 1, SAE_STATE_CONFIRMED = 2, SAE_STATE_ACCEPTED = 3, }; struct sae_sm { struct auth_proto ap; struct handshake_state *handshake; struct l_ecc_point *pwe; enum sae_state state; const struct l_ecc_curve *curve; unsigned int group; uint8_t group_retry; const unsigned int *ecc_groups; struct l_ecc_scalar *rand; struct l_ecc_scalar *scalar; struct l_ecc_scalar *p_scalar; struct l_ecc_point *element; struct l_ecc_point *p_element; uint16_t send_confirm; uint8_t kck[32]; uint8_t pmk[32]; uint8_t pmkid[16]; uint8_t *token; size_t token_len; /* number of state resyncs that have occurred */ uint16_t sync; /* number of SAE confirm messages that have been sent */ uint16_t sc; /* received value of the send-confirm counter */ uint16_t rc; /* remote peer */ uint8_t peer[6]; uint8_t assoc_retry; sae_tx_authenticate_func_t tx_auth; sae_tx_associate_func_t tx_assoc; void *user_data; }; static bool sae_pwd_seed(const uint8_t *addr1, const uint8_t *addr2, uint8_t *base, size_t base_len, uint8_t counter, uint8_t *out) { uint8_t key[12]; if (memcmp(addr1, addr2, 6) > 0) { memcpy(key, addr1, 6); memcpy(key + 6, addr2, 6); } else { memcpy(key, addr2, 6); memcpy(key + 6, addr1, 6); } return hkdf_extract(L_CHECKSUM_SHA256, key, 12, 2, out, base, base_len, &counter, (size_t) 1); } /* * Computes KDF-256(pwd_seed, "SAE Hunting and Pecking", p). If the output is * greater than p, the output is set to qnr, a quadratic non-residue. * Since this happens with very low probability, using the same qnr is fine. */ static struct l_ecc_scalar *sae_pwd_value(const struct l_ecc_curve *curve, uint8_t *pwd_seed, uint8_t *qnr) { uint8_t pwd_value[L_ECC_SCALAR_MAX_BYTES]; uint8_t prime[L_ECC_SCALAR_MAX_BYTES]; ssize_t len; int is_in_range; struct l_ecc_scalar *p = l_ecc_curve_get_prime(curve); len = l_ecc_scalar_get_data(p, prime, sizeof(prime)); l_ecc_scalar_free(p); if (!kdf_sha256(pwd_seed, 32, "SAE Hunting and Pecking", strlen("SAE Hunting and Pecking"), prime, len, pwd_value, len)) return NULL; /* * If pwd_value >= prime, this iteration should fail. We need a smooth * control flow, so we need to continue anyway. */ is_in_range = l_secure_memcmp(pwd_value, prime, len); /* * We only consider is_in_range == -1 as valid, meaning the value of the * MSB defines the mask. */ is_in_range = util_secure_fill_with_msb(is_in_range); /* * libell has public Legendre symbol only for l_ecc_scalar, but they * cannot be created if the coordinate is greater than the p. Hence, * to avoid control flow dependencies, we replace pwd_value by a dummy * quadratic non residue if we generate a value >= prime. */ util_secure_select((uint8_t) is_in_range, pwd_value, qnr, pwd_value, sizeof(pwd_value)); return l_ecc_scalar_new(curve, pwd_value, sizeof(pwd_value)); } /* IEEE 802.11-2016 - Section 12.4.2 Assumptions on SAE */ static bool sae_cn(const uint8_t *kck, uint16_t send_confirm, struct l_ecc_scalar *scalar1, struct l_ecc_point *element1, struct l_ecc_scalar *scalar2, struct l_ecc_point *element2, uint8_t *confirm) { uint8_t s1[L_ECC_SCALAR_MAX_BYTES]; uint8_t s2[L_ECC_SCALAR_MAX_BYTES]; uint8_t e1[L_ECC_POINT_MAX_BYTES]; uint8_t e2[L_ECC_POINT_MAX_BYTES]; struct l_checksum *hmac; struct iovec iov[5]; int ret; hmac = l_checksum_new_hmac(L_CHECKSUM_SHA256, kck, 32); if (!hmac) return false; iov[0].iov_base = &send_confirm; iov[0].iov_len = 2; iov[1].iov_base = (void *) s1; iov[1].iov_len = l_ecc_scalar_get_data(scalar1, s1, sizeof(s1)); iov[2].iov_base = (void *) e1; iov[2].iov_len = l_ecc_point_get_data(element1, e1, sizeof(e1)); iov[3].iov_base = (void *) s2; iov[3].iov_len = l_ecc_scalar_get_data(scalar2, s2, sizeof(s2)); iov[4].iov_base = (void *) e2; iov[4].iov_len = l_ecc_point_get_data(element2, e2, sizeof(e2)); l_checksum_updatev(hmac, iov, 5); ret = l_checksum_get_digest(hmac, confirm, 32); l_checksum_free(hmac); return (ret == 32); } static void sae_reject_authentication(struct sae_sm *sm, uint16_t reason) { uint8_t reject[6]; uint8_t *ptr = reject; /* transaction */ l_put_u16(1, ptr); ptr += 2; /* status success */ l_put_u16(reason, ptr); ptr += 2; if (reason == MMPDU_STATUS_CODE_UNSUPP_FINITE_CYCLIC_GROUP) { l_put_u16(sm->group, ptr); ptr += 2; } sm->tx_auth(reject, ptr - reject, sm->user_data); } static struct l_ecc_scalar *sae_new_residue(const struct l_ecc_curve *curve, bool residue) { struct l_ecc_scalar *s = l_ecc_scalar_new_random(curve); while (l_ecc_scalar_legendre(s) != ((residue) ? -1 : 1)) { l_ecc_scalar_free(s); s = l_ecc_scalar_new_random(curve); } return s; } static uint8_t sae_is_quadradic_residue(const struct l_ecc_curve *curve, struct l_ecc_scalar *value, struct l_ecc_scalar *qr, struct l_ecc_scalar *qnr) { uint64_t rbuf[L_ECC_MAX_DIGITS]; struct l_ecc_scalar *y_sqr = l_ecc_scalar_new(curve, NULL, 0); struct l_ecc_scalar *r = l_ecc_scalar_new_random(curve); struct l_ecc_scalar *num = l_ecc_scalar_new(curve, NULL, 0); size_t bytes; l_ecc_scalar_sum_x(y_sqr, value); l_ecc_scalar_multiply(num, y_sqr, r); l_ecc_scalar_multiply(num, num, r); l_ecc_scalar_free(y_sqr); bytes = l_ecc_scalar_get_data(r, rbuf, sizeof(rbuf)); l_ecc_scalar_free(r); if (bytes <= 0) { l_ecc_scalar_free(num); return 0; } if (rbuf[bytes / 8 - 1] & 1) { l_ecc_scalar_multiply(num, num, qr); if (l_ecc_scalar_legendre(num) == -1) { l_ecc_scalar_free(num); return 1; } } else { l_ecc_scalar_multiply(num, num, qnr); if (l_ecc_scalar_legendre(num) == 1) { l_ecc_scalar_free(num); return 1; } } l_ecc_scalar_free(num); return 0; } /* * IEEE 802.11-2016 Section 12.4.4.2.2 * Generation of the password element with ECC groups */ static struct l_ecc_point *sae_compute_pwe(const struct l_ecc_curve *curve, const char *password, const uint8_t *addr1, const uint8_t *addr2) { uint8_t found = 0; uint8_t is_residue; uint8_t is_odd = 0; uint8_t counter; uint8_t pwd_seed[32]; uint8_t x[L_ECC_SCALAR_MAX_BYTES]; uint8_t x_cand[L_ECC_SCALAR_MAX_BYTES]; struct l_ecc_scalar *pwd_value; uint8_t *dummy; uint8_t *base; size_t base_len; struct l_ecc_scalar *qr; struct l_ecc_scalar *qnr; uint8_t qnr_bin[L_ECC_SCALAR_MAX_BYTES] = {0}; struct l_ecc_point *pwe; /* create qr/qnr prior to beginning hunting-and-pecking loop */ qr = sae_new_residue(curve, true); qnr = sae_new_residue(curve, false); l_ecc_scalar_get_data(qnr, qnr_bin, sizeof(qnr_bin)); /* * Allocate memory for the base, and set a random dummy to be used in * additional iterations, once a valid value is found */ base_len = strlen(password); base = l_malloc(base_len * sizeof(*base)); dummy = l_malloc(base_len * sizeof(*dummy)); l_getrandom(dummy, base_len); /* * Loop with constant time and memory access * We do 30 iterations instead of the 40 recommended to achieve a * resonnable security/complexity trade-off. */ for (counter = 1; counter <= 30; counter++) { /* * Set base to either dummy or password, depending on found's * value. * A non-secure version would be: * base = (found ? dummy : password); */ util_secure_select(found, dummy, (uint8_t *)password, base, base_len); /* * pwd-seed = H(max(addr1, addr2) || min(addr1, addr2), * base || counter) * pwd-value = KDF-256(pwd-seed, "SAE Hunting and Pecking", p) */ sae_pwd_seed(addr1, addr2, base, base_len, counter, pwd_seed); /* * The case pwd_value > prime is handled inside, so that * execution can continue whatever the result is, without * changing the outcome. */ pwd_value = sae_pwd_value(curve, pwd_seed, qnr_bin); /* * Check if the candidate is a valid x-coordinate on our curve, * and convert it from scalar to binary. */ is_residue = sae_is_quadradic_residue(curve, pwd_value, qr, qnr); l_ecc_scalar_get_data(pwd_value, x_cand, sizeof(x_cand)); /* * If we already found the point, we overwrite x with itself. * Otherwise, we copy the new candidate into x. */ util_secure_select(found, x, x_cand, x, sizeof(x)); is_odd = util_secure_select_byte(found, is_odd, pwd_seed[31] & 0x01); /* * found is 0 or 0xff here and is_residue is 0 or 1. Bitwise OR * of them (with is_residue converted to 0/0xff) handles this * in constant time. */ found |= is_residue * 0xff; memset(pwd_seed, 0, sizeof(pwd_seed)); l_ecc_scalar_free(pwd_value); } l_ecc_scalar_free(qr); l_ecc_scalar_free(qnr); l_free(dummy); l_free(base); if (!found) { l_error("max PWE iterations reached!"); return NULL; } pwe = l_ecc_point_from_data(curve, !is_odd + 2, x, sizeof(x)); if (!pwe) l_error("computing y failed, was x quadratic residue?"); return pwe; } static bool sae_build_commit(struct sae_sm *sm, const uint8_t *addr1, const uint8_t *addr2, uint8_t *commit, size_t *len, bool retry) { struct l_ecc_scalar *mask; uint8_t *ptr = commit; struct l_ecc_scalar *order; if (retry) goto old_commit; if (!sm->handshake->passphrase) { l_error("no handshake passphrase found"); return false; } sm->pwe = sae_compute_pwe(sm->curve, sm->handshake->passphrase, addr1, addr2); if (!sm->pwe) { l_error("could not compute PWE"); return false; } sm->scalar = l_ecc_scalar_new(sm->curve, NULL, 0); sm->rand = l_ecc_scalar_new_random(sm->curve); mask = l_ecc_scalar_new_random(sm->curve); order = l_ecc_curve_get_order(sm->curve); /* commit-scalar = (rand + mask) mod r */ l_ecc_scalar_add(sm->scalar, sm->rand, mask, order); l_ecc_scalar_free(order); /* commit-element = inv(mask * PWE) */ sm->element = l_ecc_point_new(sm->curve); l_ecc_point_multiply(sm->element, mask, sm->pwe); l_ecc_point_inverse(sm->element); l_ecc_scalar_free(mask); /* * Several cases require retransmitting the same commit message. The * anti-clogging code path requires this as well as the retransmission * timeout. */ old_commit: /* transaction */ l_put_le16(1, ptr); ptr += 2; /* status success */ l_put_le16(0, ptr); ptr += 2; /* group */ l_put_le16(sm->group, ptr); ptr += 2; if (sm->token) { memcpy(ptr, sm->token, sm->token_len); ptr += sm->token_len; } ptr += l_ecc_scalar_get_data(sm->scalar, ptr, L_ECC_SCALAR_MAX_BYTES); ptr += l_ecc_point_get_data(sm->element, ptr, L_ECC_POINT_MAX_BYTES); *len = ptr - commit; return true; } static void sae_send_confirm(struct sae_sm *sm) { uint8_t confirm[32]; uint8_t body[38]; uint8_t *ptr = body; /* * confirm = CN(KCK, send-confirm, commit-scalar, COMMIT-ELEMENT, * peer-commit-scalar, PEER-COMMIT-ELEMENT) */ sae_cn(sm->kck, sm->sc, sm->scalar, sm->element, sm->p_scalar, sm->p_element, confirm); l_put_le16(2, ptr); ptr += 2; l_put_le16(0, ptr); ptr += 2; l_put_le16(sm->sc, ptr); ptr += 2; memcpy(ptr, confirm, 32); ptr += 32; sm->state = SAE_STATE_CONFIRMED; sm->tx_auth(body, 38, sm->user_data); } static int sae_process_commit(struct sae_sm *sm, const uint8_t *from, const uint8_t *frame, size_t len) { uint8_t *ptr = (uint8_t *) frame; uint8_t k[L_ECC_SCALAR_MAX_BYTES]; struct l_ecc_point *k_point; uint8_t zero_key[32] = { 0 }; uint8_t keyseed[32]; uint8_t kck_and_pmk[2][32]; uint8_t tmp[L_ECC_SCALAR_MAX_BYTES]; struct l_ecc_scalar *tmp_scalar; uint16_t group; uint16_t reason = MMPDU_REASON_CODE_UNSPECIFIED; ssize_t klen; struct l_ecc_scalar *order; unsigned int nbytes = l_ecc_curve_get_scalar_bytes(sm->curve); if (sm->state != SAE_STATE_COMMITTED) { l_error("bad state %u", sm->state); goto reject; } /* Scalar + Point + group */ if (len < nbytes + nbytes * 2 + 2) { l_error("bad packet length"); goto reject; } group = l_get_le16(ptr); ptr += 2; if (group != sm->group) { sae_reject_authentication(sm, MMPDU_STATUS_CODE_UNSUPP_FINITE_CYCLIC_GROUP); return 0; } sm->p_scalar = l_ecc_scalar_new(sm->curve, ptr, nbytes); if (!sm->p_scalar) { l_error("Server sent invalid P_Scalar during commit"); reason = MMPDU_REASON_CODE_UNSPECIFIED; goto reject; } ptr += nbytes; sm->p_element = l_ecc_point_from_data(sm->curve, L_ECC_POINT_TYPE_FULL, ptr, nbytes * 2); if (!sm->p_element) { l_error("Server sent invalid P_Element during commit"); reason = MMPDU_REASON_CODE_UNSPECIFIED; goto reject; } if (l_ecc_scalars_are_equal(sm->p_scalar, sm->scalar) || l_ecc_points_are_equal(sm->p_element, sm->element)) { /* possible reflection attack, silently discard message */ l_warn("peer scalar or element matched own, discarding frame"); return 0; } sm->sc++; /* * K = scalar-op(rand, (element-op(scalar-op(peer-commit-scalar, PWE), * PEER-COMMIT-ELEMENT))) */ k_point = l_ecc_point_new(sm->curve); /* k_point = scalar-op(peer-commit-scalar, PWE) */ l_ecc_point_multiply(k_point, sm->p_scalar, sm->pwe); /* k_point = element-op(k_point, PEER-COMMIT-ELEMENT) */ l_ecc_point_add(k_point, k_point, sm->p_element); /* k_point = scalar-op(rand, k_point) */ l_ecc_point_multiply(k_point, sm->rand, k_point); /* * IEEE 802.11-2016 - Section 12.4.4.2.1 ECC group definition * ECC groups make use of a mapping function, F, that maps a * point (x, y) that satisfies the curve equation to its x-coordinate- * i.e., if P = (x, y) then F(P) = x. */ klen = l_ecc_point_get_x(k_point, k, sizeof(k)); l_ecc_point_free(k_point); if (klen < 0) goto reject; /* keyseed = H(<0>32, k) */ hmac_sha256(zero_key, 32, k, klen, keyseed, 32); /* * kck_and_pmk = KDF-Hash-512(keyseed, "SAE KCK and PMK", (commit-scalar + peer-commit-scalar) mod r) */ tmp_scalar = l_ecc_scalar_new(sm->curve, NULL, 0); order = l_ecc_curve_get_order(sm->curve); l_ecc_scalar_add(tmp_scalar, sm->p_scalar, sm->scalar, order); l_ecc_scalar_get_data(tmp_scalar, tmp, sizeof(tmp)); kdf_sha256(keyseed, 32, "SAE KCK and PMK", strlen("SAE KCK and PMK"), tmp, nbytes, kck_and_pmk, 64); memcpy(sm->kck, kck_and_pmk[0], 32); memcpy(sm->pmk, kck_and_pmk[1], 32); /* * PMKID = L((commit-scalar + peer-commit-scalar) mod r, 0, 128) */ l_ecc_scalar_add(tmp_scalar, sm->scalar, sm->p_scalar, order); l_ecc_scalar_get_data(tmp_scalar, tmp, sizeof(tmp)); l_ecc_scalar_free(order); l_ecc_scalar_free(tmp_scalar); /* don't set the handshakes pmkid until confirm is verified */ memcpy(sm->pmkid, tmp, 16); sae_send_confirm(sm); return 0; reject: sae_reject_authentication(sm, reason); return -EBADMSG; } static bool sae_verify_confirm(struct sae_sm *sm, const uint8_t *frame) { uint8_t check[32]; uint16_t rc = l_get_le16(frame); sae_cn(sm->kck, rc, sm->p_scalar, sm->p_element, sm->scalar, sm->element, check); if (memcmp(frame + 2, check, 32)) { l_error("confirm did not match"); return false; } sm->rc = rc; return true; } static int sae_process_confirm(struct sae_sm *sm, const uint8_t *from, const uint8_t *frame, size_t len) { const uint8_t *ptr = frame; if (sm->state != SAE_STATE_CONFIRMED) { l_error("bad state %u", sm->state); goto reject; } if (len < 34) { l_error("bad length"); goto reject; } if (!sae_verify_confirm(sm, ptr)) goto reject; /* Sc shall be set to the value 2^16 - 1 */ sm->sc = 0xffff; handshake_state_set_pmkid(sm->handshake, sm->pmkid); handshake_state_set_pmk(sm->handshake, sm->pmk, 32); sm->state = SAE_STATE_ACCEPTED; sm->tx_assoc(sm->user_data); return 0; reject: sae_reject_authentication(sm, MMPDU_REASON_CODE_UNSPECIFIED); return -EBADMSG; } static bool sae_send_commit(struct sae_sm *sm, bool retry) { struct handshake_state *hs = sm->handshake; /* regular commit + possible 256 byte token + 6 bytes header */ uint8_t commit[L_ECC_SCALAR_MAX_BYTES + L_ECC_POINT_MAX_BYTES + 262]; size_t len; if (!sae_build_commit(sm, hs->spa, hs->aa, commit, &len, retry)) return false; sm->state = SAE_STATE_COMMITTED; sm->tx_auth(commit, len, sm->user_data); return true; } static bool sae_assoc_timeout(struct auth_proto *ap) { struct sae_sm *sm = l_container_of(ap, struct sae_sm, ap); if (sm->assoc_retry >= SAE_MAX_ASSOC_RETRY) return false; sm->assoc_retry++; sm->tx_assoc(sm->user_data); return true; } /* * 802.11-2016 - Section 12.4.8.6.4 * If the Status code is ANTI_CLOGGING_TOKEN_REQUIRED, a new SAE Commit message * shall be constructed with the Anti-Clogging Token from the received * Authentication frame, and the commit-scalar and COMMIT-ELEMENT previously * sent. The new SAE Commit message shall be transmitted to the peer, Sync shall * be zeroed, and the t0 (retransmission) timer shall be set. */ static void sae_process_anti_clogging(struct sae_sm *sm, const uint8_t *ptr, size_t len) { /* * IEEE 802.11-2016 - Section 12.4.6 Anti-clogging tokens * * "It is suggested that an Anti-Clogging Token not exceed 256 octets" * * Also ensure the token is at least 1 byte. The packet passed in will * contain the group number, meaning the anti-clogging token length is * going to be 2 bytes less than the passed in length. This is why we * are checking 3 > len > 258. */ if (len < 3 || len > 258) { l_error("anti-clogging token size invalid %zu", len); return; } sm->token = l_memdup(ptr + 2, len - 2); sm->token_len = len - 2; sm->sync = 0; sae_send_commit(sm, true); } /* * 802.11-2016 - 12.4.8.6.3 Protocol instance behavior - Nothing state */ static int sae_verify_nothing(struct sae_sm *sm, uint16_t transaction, uint16_t status, const uint8_t *frame, size_t len) { /* * TODO: This does not handle the transition from NOTHING -> CONFIRMED * as this is only relevant to the AP or in Mesh mode which is not * yet supported. */ if (transaction != SAE_STATE_COMMITTED) return -EBADMSG; /* frame shall be silently discarded and Del event sent */ if (status != 0) return -EBADMSG; if (len < 2) return -EBADMSG; /* reject with unsupported group */ if (l_get_le16(frame) != sm->group) { sae_reject_authentication(sm, MMPDU_STATUS_CODE_UNSUPP_FINITE_CYCLIC_GROUP); return -EBADMSG; } return 0; } static void sae_reset_state(struct sae_sm *sm) { l_free(sm->token); sm->token = NULL; l_ecc_scalar_free(sm->scalar); sm->scalar = NULL; l_ecc_scalar_free(sm->p_scalar); sm->p_scalar = NULL; l_ecc_scalar_free(sm->rand); sm->rand = NULL; l_ecc_point_free(sm->element); sm->element = NULL; l_ecc_point_free(sm->p_element); sm->p_element = NULL; l_ecc_point_free(sm->pwe); sm->pwe = NULL; } /* * 802.11-2016 - 12.4.8.6.4 Protocol instance behavior - Committed state */ static int sae_verify_committed(struct sae_sm *sm, uint16_t transaction, uint16_t status, const uint8_t *frame, size_t len) { /* * Upon receipt of a Con event... * Then the protocol instance checks the value of Sync. If it * is greater than dot11RSNASAESync, the protocol instance shall send a * Del event to the parent process and transition back to Nothing state. * If Sync is not greater than dot11RSNASAESync, the protocol instance * shall increment Sync, transmit the last SAE Commit message sent to * the peer... */ if (transaction == SAE_STATE_CONFIRMED) { if (sm->sync > SAE_SYNC_MAX) return -EBADMSG; sm->sync++; sae_send_commit(sm, true); return -EAGAIN; } switch (status) { case MMPDU_STATUS_CODE_ANTI_CLOGGING_TOKEN_REQ: sae_process_anti_clogging(sm, frame, len); return -EAGAIN; case MMPDU_STATUS_CODE_UNSUPP_FINITE_CYCLIC_GROUP: /* * TODO: hostapd in its current state does not include the * group number as it should. This is a violation of the spec, * but there isn't much we can do about it. We simply treat this * response as if its rejecting our last commit message (which * it most likely is). If/When this is fixed we should be * checking that the group matches here, e.g. * * if (l_get_le16(frame) != sm->group) * return false; * * According to 802.11 Section 12.4.8.6.4: * * "If the rejected group does not match the last offered group * the protocol instance shall silently discard the message and * set the t0 (retransmission) timer" */ if (len == 0) l_warn("AP did not include group number in response!"); else if (len >= 2 && (l_get_le16(frame) != sm->group)) return -EBADMSG; sm->group_retry++; if (sm->ecc_groups[sm->group_retry] == 0) { /* * "If there are no other groups to choose, the protocol * instance shall send a Del event to the parent process * and transitions back to Nothing state" */ sm->state = SAE_STATE_NOTHING; goto reject_unsupp_group; } /* * "If the rejected group matches the last offered group, the * protocol instance shall choose a different group and generate * the PWE and the secret values according to 12.4.5.2; it then * generates and transmits a new SAE Commit message to the peer, * zeros Sync, sets the t0 (retransmission) timer, and remains * in Committed state" */ sae_reset_state(sm); sm->group = sm->ecc_groups[sm->group_retry]; sm->curve = l_ecc_curve_from_ike_group(sm->group); sm->sync = 0; sae_send_commit(sm, false); return -EAGAIN; case 0: if (len < 2) return -EBADMSG; if (l_get_le16(frame) == sm->group) return 0; if (!l_ecc_curve_from_ike_group(l_get_le16(frame))) { if (sm->sync > SAE_SYNC_MAX) return -EBADMSG; sm->sync++; goto reject_unsupp_group; } /* * If we get here we know that the groups do not match, but the * group provided in the frame is supported. From section * 12.4.8.6.4 we see: * * "If the group is supported but does not match that used when * the protocol instance constructed its SAE Commit message, * DiffGrp shall be set and the local identity and peer identity * shall be checked" */ if (memcmp(sm->handshake->spa, sm->handshake->aa, 6) > 0) { /* * "The mesh STA, with the numerically greater of the two * MAC addresses, drops the received SAE Commit message, * retransmits its last SAE Commit message, and shall * set the t0 (retransmission) timer and remain in * Committed state" */ sae_send_commit(sm, true); return 0; } /* * "The mesh STA, with the numerically lesser of the two * MAC addresses, zeros Sync, shall increment Sc, choose * the group from the received SAE Commit message, * generate new PWE and new secret values according to * 12.4.5.2, process the received SAE Commit message * according to 12.4.5.4, generate a new SAE Commit * message and SAE Confirm message, and shall transmit * the new Commit and Confirm to the peer. It shall then * transition to Confirmed state." */ sm->sync = 0; sm->sc++; sm->group = l_get_le16(frame); sm->curve = l_ecc_curve_from_ike_group(sm->group); sae_send_commit(sm, false); sm->state = SAE_STATE_CONFIRMED; /* * The processing and sending of the confirm message * will happen after we return. Since we have set the * state to CONFIRMED, our confirm handler will get * called. */ return 0; default: /* * If the Status is some other nonzero value, the frame shall * be silently discarded... */ return 0; } reject_unsupp_group: sae_reject_authentication(sm, MMPDU_STATUS_CODE_UNSUPP_FINITE_CYCLIC_GROUP); return MMPDU_STATUS_CODE_UNSUPP_FINITE_CYCLIC_GROUP; } /* * 802.11-2016 - 12.4.8.6.5 Protocol instance behavior - Confirmed state */ static int sae_verify_confirmed(struct sae_sm *sm, uint16_t trans, uint16_t status, const uint8_t *frame, size_t len) { if (trans == SAE_STATE_CONFIRMED) return 0; /* * If the Status is nonzero, the frame shall be silently discarded... */ if (status != 0) return 0; /* * If Sync is greater than dot11RSNASAESync, the protocol instance * shall send the parent process a Del event and transitions back to * Nothing state. */ if (sm->sync > SAE_SYNC_MAX) return -EBADMSG; if (len < 2) return -EBADMSG; /* frame shall be silently discarded */ if (l_get_le16(frame) != sm->group) return 0; /* * the protocol instance shall increment Sync, increment Sc, and * transmit its Commit and Confirm (with the new Sc value) messages. */ sm->sync++; sm->sc++; sae_send_commit(sm, true); sae_send_confirm(sm); return 0; } /* * 802.11-2016 - 12.4.8.6.6 Protocol instance behavior - Accepted state */ static int sae_verify_accepted(struct sae_sm *sm, uint16_t trans, uint16_t status, const uint8_t *frame, size_t len) { uint16_t sc; /* spec does not specify what to do here, so print and discard */ if (trans != SAE_STATE_CONFIRMED) { l_error("received transaction %u in accepted state", trans); return -EBADMSG; } if (sm->sync > SAE_SYNC_MAX) return -EBADMSG; if (len < 2) return -EBADMSG; sc = l_get_le16(frame); /* * ... the value of send-confirm shall be checked. If the value is not * greater than Rc or is equal to 2^16 - 1, the received frame shall be * silently discarded. */ if (sc <= sm->rc || sc == 0xffff) return -EBADMSG; /* * If the verification fails, the received frame shall be silently * discarded. */ if (!sae_verify_confirm(sm, frame)) return -EBADMSG; /* * If the verification succeeds, the Rc variable shall be set to the * send-confirm portion of the frame, the Sync shall be incremented and * a new SAE Confirm message shall be constructed (with Sc set to * 2^16 - 1) and sent to the peer. */ sm->sync++; sm->sc = 0xffff; sae_send_confirm(sm); return 0; } static int sae_verify_packet(struct sae_sm *sm, uint16_t trans, uint16_t status, const uint8_t *frame, size_t len) { if (trans != SAE_STATE_COMMITTED && trans != SAE_STATE_CONFIRMED) return -EBADMSG; switch (sm->state) { case SAE_STATE_NOTHING: return sae_verify_nothing(sm, trans, status, frame, len); case SAE_STATE_COMMITTED: return sae_verify_committed(sm, trans, status, frame, len); case SAE_STATE_CONFIRMED: return sae_verify_confirmed(sm, trans, status, frame, len); case SAE_STATE_ACCEPTED: return sae_verify_accepted(sm, trans, status, frame, len); } /* should never get here */ return -1; } static int sae_rx_authenticate(struct auth_proto *ap, const uint8_t *frame, size_t len) { struct sae_sm *sm = l_container_of(ap, struct sae_sm, ap); const struct mmpdu_header *hdr = mpdu_validate(frame, len); const struct mmpdu_authentication *auth; int ret; if (!hdr) { l_debug("Auth frame header did not validate"); goto reject; } auth = mmpdu_body(hdr); len -= mmpdu_header_len(hdr); ret = sae_verify_packet(sm, L_LE16_TO_CPU(auth->transaction_sequence), L_LE16_TO_CPU(auth->status), auth->ies, len - 6); if (ret != 0) return ret; switch (L_LE16_TO_CPU(auth->transaction_sequence)) { case SAE_STATE_COMMITTED: return sae_process_commit(sm, hdr->address_2, auth->ies, len - 6); case SAE_STATE_CONFIRMED: return sae_process_confirm(sm, hdr->address_2, auth->ies, len - 6); default: l_error("invalid transaction sequence %u", L_LE16_TO_CPU(auth->transaction_sequence)); } reject: sae_reject_authentication(sm, MMPDU_REASON_CODE_UNSPECIFIED); return -EBADMSG; } static int sae_rx_associate(struct auth_proto *ap, const uint8_t *frame, size_t len) { const struct mmpdu_header *mpdu = NULL; const struct mmpdu_association_response *body; mpdu = mpdu_validate(frame, len); if (!mpdu) { l_error("could not process frame"); return -EBADMSG; } body = mmpdu_body(mpdu); if (body->status_code != 0) return L_LE16_TO_CPU(body->status_code); return 0; } static bool sae_start(struct auth_proto *ap) { struct sae_sm *sm = l_container_of(ap, struct sae_sm, ap); if (sm->handshake->authenticator) memcpy(sm->peer, sm->handshake->spa, 6); else memcpy(sm->peer, sm->handshake->aa, 6); return sae_send_commit(sm, false); } static void sae_free(struct auth_proto *ap) { struct sae_sm *sm = l_container_of(ap, struct sae_sm, ap); sae_reset_state(sm); /* zero out whole structure, including keys */ explicit_bzero(sm, sizeof(struct sae_sm)); l_free(sm); } struct auth_proto *sae_sm_new(struct handshake_state *hs, sae_tx_authenticate_func_t tx_auth, sae_tx_associate_func_t tx_assoc, void *user_data) { struct sae_sm *sm; sm = l_new(struct sae_sm, 1); if (!sm) return NULL; sm->tx_auth = tx_auth; sm->tx_assoc = tx_assoc; sm->user_data = user_data; sm->handshake = hs; sm->state = SAE_STATE_NOTHING; sm->ecc_groups = l_ecc_supported_ike_groups(); sm->group = sm->ecc_groups[sm->group_retry]; sm->curve = l_ecc_curve_from_ike_group(sm->group); sm->ap.start = sae_start; sm->ap.free = sae_free; sm->ap.rx_authenticate = sae_rx_authenticate; sm->ap.rx_associate = sae_rx_associate; sm->ap.assoc_timeout = sae_assoc_timeout; return &sm->ap; }